Etching is today a commonly used technique in the production of printed circuit boards. In the production of a printed circuit board, a substrate such as a plastic laminate is coated with a layer of conducting material such as copper. On top of the copper layer, a protective layer of e.g. an organic polymer is provided photochemically to selectively cover certain parts of the copper layer. The coated substrate is etched in an etching machine in which the coated substrate is exposed to a continuous flow of copper etching solution, thereby etching away at least a portion of the copper layer not covered by the protective layer, leaving the protected portions of the copper layer non-etched to produce the conductive layer of the printed circuit board.
In a conventional etching process an oxidizing agent, such as for example hydrogen peroxide, sodium chlorate or gas comprising ozon or chlorine gas, is used for reoxidizing the used copper etching solution in the etching machine. Such oxidizing agents are, however, considered aggressive chemical compounds which negatively affect the working environment and the environment in a broader perspective.
EP 0048381 B1 teaches an alternative process for regeneration of hydrochloric acid copper chloride copper etching solution, wherein etching and regenerating is effected in separate devices between which the copper etching solution is circulated. The copper etching solution is sucked from the etching machine and sprayed into a bell comprising oxygen gas.
Despite of the alternative process in EP 0048381 B1, there is still a need in the art for improved processes of regenerating copper in a copper etching solution.